Undefined Reference Error

I am getting an Undefined reference to <function>, here is my code:

Code:

---

#include <stdio.h>
#include "qsolver.h"


int main() {
        double a, b, c, x1, x2;
        int qret;

        while(1) {
                printf("Enter variables for quadratic equation (type: \n");
                scanf("%lf %lf %lf", &a, &b, &c);

                if((qret = qsolver(a, b, c, &x1, &x2)) != 0) {
                        printf("Error Value:  %d\n", qret);
                }
        }
        return 0;
}

******************************************************************************

#include <stdio.h>
#include <math.h>
#include "qsolver.h"

int qsolver(double a, double b, double c, double* x1, double* x2) {

        //Is the user giving an input which would divide by zero?
        if(a == 0) {
                printf("Input Not A Quadratic; Cannot Have Value Of '0' For A\n");
                return 1;
        }

        //Is the user giving and input which would try to compute a square root of a negative number.
        else if( (4*a*c) > pow(b,2) ) {
                printf("There Are No Real Solutions; B^2 Is Less Than (4*A*C)\n");
                return 2;
        }

        //The user input is valid, solve accordingly
        else {
                *x1 = (-b + sqrt(pow(b,2) - (4*a*c)))/(2*a);
                *x2 = (-b - sqrt(pow(b,2) - (4*a*c)))/(2*a);
               
                return 0;
        }
}

*****************************************************************************************

#ifndef QSOLVER_H
#define QSOLVER_H

int qsolver(double, double, double, double *, double *);

#endif

---

You'll have to compile all your .c files and link them together. (Most people don't actually run the linker separately; usually your compiler will do it for you, but you have to compile your .c files together.)

I have a Makefile I am using to link the files together but I am still getting the error. If you would like I can post that also

Well, that wouldn't hurt.

Instead of <function> why not tell us which function it actually is? I suspect you're not linking with the math library.

The function is qsolver; here is the code to the makefile also which I believe links the math library:

Code:

---

CC = gcc
CFLAGS= -Wall -pedantic

q:  q.o q.solver.o
        ${CC} -o q q.o qsolver.o -lm
q.o:  q.s
        ${CC} -c q.s
qsolver.o:  qsolver.s
        ${CC} -c qsolver.s
q.s:  q.c qsolver.h
        ${CC} ${CFLAGS} -s q.c
qsolver.s:  qsolver.c qsolver.h
        ${CC} ${CFLAGS} -s qsolver.c
clean:
        rm -f *.o *.s q core

---

Code:

---

q:  q.o q.solver.o

---

Shouldn't q.solver.o be qsolver.o?

Quote:

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Originally Posted by NuNn

The function is qsolver; here is the code to the makefile also which I believe links the math library:

---

Well, I think your problem is in your makefile. Why are you compiling to ASSEMBLY first? Also, you say that "q" depends on something called "q.solver.o", yet you link with qsolver.o -- that means that qsolver.o will not get rebuilt because it's not listed as a dependency.

Surely your linker is also printing some error like "Can't find qsolver.o"

Try this:

Code:

---

CC = gcc
CFLAGS= -Wall -pedantic

q:  q.o qsolver.o
        $(CC) -o $@ $^ -lm

q.o:  q.c

qsolver.o:  qsolver.c

clean:
        rm -f *.o q core

---

Yep, typo on my part with the q.solver.o

brewbuck: Thank you that fixed the problem. Could you tell me what the "$@ $^" symbols mean?

Quote:

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Originally Posted by NuNn

Yep, typo on my part but the "undefined reference" still remains

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So you admit the makefile you posted is not the actual makefile. I don't want to waste my time speculating when you won't show the real stuff.

Brewbuck what are you talking about????? That was my actual makefile. No need to get offensive here. I was thanking you for fixing my problem.............

Quote:

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Originally Posted by NuNn

Brewbuck what are you talking about????? That was my actual makefile. No need to get offensive here. I was thanking you for fixing my problem.............

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I misunderstood you. I thought you meant you made a typo while retyping the makefile to post to the forum, and I hate it when people retype instead of copy-pasting. Sorry.

The special variable $@ means "the target", i.e. the thing on the left side of the colon. The variable $^ means "the dependencies," i.e. everything to the right of the colon. It makes maintenance of your makefile easier, because when you add a dependency you don't have to update the rule.

There are other specials, like $? which means "only the dependencies which have actually changed."

Alrighty, thank you very much for your help. Otherwise I would have been sitting thinking for a while trying to figure it out haha.